The spectral information processing of the primate visual system will be measured by two techniques: hue discrimination and increment-threshold spectral sensitivity on rhesus monkeys and normal and anomalous trichromatic human subjects. Different conditions of adaptation and of recovery from induced dichromacy have been selected to reveal the relationship between cone response and the color discrimination mechanism. In addition, hue discrimination data will provide needed information to further assess important differences between red- and green-sensitive cone response functions and will help to relate induced dichromacy to congenital dichromacy (color-blindness).